::For nothing can seem foul to those that win::

 <script language=javascript>
function value_up(obj){
if(obj != null)
    {
        if(obj.value=="" || isNaN(obj.value))return false;
        var val = obj.value;
        val++;
        obj.value =val;
    } 
}
function value_down(obj){
if(obj !=null)
    {
        if(obj.value=="" || isNaN(obj.value))return false;
        var val = obj.value;
        val--;
        obj.value =val;
    }
}
</script>

   调用方法：

<input type="button" value="up" onClick="value_up('文本框ID')">

    （完）